Final answer:
The statement is true; when defining a function, you need to specify both the data types and the identifiers for each parameter so that the function can be properly implemented and used.
Step-by-step explanation:
The statement that a function definition requires the data types and identifiers for each parameter is true. When defining a function in most programming languages, you must specify the data type for each parameter to inform the compiler or interpreter what kind of data it should expect. Identifiers or variable names are also needed so that you can reference these parameters within the function's body.